docs: def read_requirements(filename):
      """
      Parse a requirements file.
  
      Accepts vcs+ links, and places the URL into
      `DEPENDENCY_LINKS`.
  
      :return: list of str for each package
      """
      data = []
      for line in read_file(filename):
          line = line.strip()
          if not line or line.startswith('#'):
              continue
  
          if '+' in line[:4]:
              repo_link, egg_name = line.split('#egg=')
              if not egg_name:
                  raise ValueError('Unknown requirement: {0}'
                                      .format(line))
  
              DEPENDENCY_LINKS.append(line)
  
              line = egg_name
  
          data.append(line)
  
      return data